This invention relates to a composition and processes therefor in which the composition comprises chelates of titanium alkoxides having low freezing points.
Titanium chelates have a number of industrial uses. They are valuable in a variety of applications such as catalysis, corrosion inhibition, crosslinking and other applications. Their formula can be depicted as (RO)2TiX2 where X is derived from a chelating agent such as, for example, 2,4-pentanedione and R is a straight or branched alkyl group. They can be made by reacting a titanium orthoester of the formula Ti(OR)4 such as, for example, tetraisopropyl titanate (also known as tetraisopropoxy titanium) with approximately two equivalents of chelating agent such as, for example, 2,4-pentanedione (also known as acetyl acetone) accompanied by the release of two equivalents of the alcohol of the formula ROH.
In such titanium chelates made from a single alcohol, the compounds may have high freezing points and be difficult to handle. Some may initially be a liquid, even remaining as a liquid even after having been supercooled to some considerable extent, but then freeze spontaneously, especially in the presence of a nucleating agent such as dust or part of the reaction product in crystal form. To prevent this, these titanium chelates may be left in the reaction solution in which they were formed, that is, still containing the byproduct alcohol rather than removing it. However this is a disadvantage when the solutions are used in industry because of the resulting low flash point of the solution and the creation of solvent pollution/disposal problems. Preferably, the titanium chelate product is essentially alcohol-free.
Mixed alcohol chelates generally have lower freezing points than chelates of a single alcohol, and are thus liquid at temperatures of typical use even with all byproduct alcohol removed. Mixed chelates can be produced from a mixture of titanium orthoesters with a chelating agent. However, when such alcohols are removed from their mixtures, it is often difficult to control the ratio of alkoxides in the resulting product. This is due to distinct alcohols having different boiling points and being retained to differing and variable extents during their removal from the reaction mass, resulting in often unpredictable and variable product compositions.
U.S. Pat. No. 4,551,544 discloses a reaction product of a titanate (OR1)4Ti, 2,4-pentanedione, and either another titanate (OR2)4Ti or an alcohol R3OH. U.S. Pat. No. 5,349,073 discloses admixing diisopropoxy titanium bis(acetylacetonate) with a dialkoxy titanium bis(acetylacetonate) to produce isopropoxyalkoxy bis(acetylacetonate) titanium.
However, the alcohol content in the known products is higher than desired. Additionally, the known process requires multiple steps. Also, many of the component chelates can freeze at typical ambient temperatures making the storage more time consuming and can require exposing the material to extended heating in order to thaw it for recharging. Such extended heating can lead to excessive color development in the products.
Therefore, a new product and a process therefor are needed in which the product comprises mixed titanium chelates, is essentially or substantially alcohol-free, and has constant and predictable composition.
According to a first embodiment of the invention, a substantially alcohol-free composition is provided, which comprises (A) TiXm(OR)4xe2x88x92m, (B) TiXm(OR)(4xe2x88x92m)/2(OR1)(4xe2x88x92m)/2, and (C) TiXm(OR1)4xe2x88x92m wherein X is a radical derived from a chelating agent comprising an organic 1,3-dicarbonyl compound; m is a number from about 1.5 to about 2.5; each R and R1 is independently a hydrocarbyl radical containing from 1 to about 10 carbon atoms per radical; and R1 differs from R.
According to a second embodiment of the invention, a process comprises (1) contacting a tetraalkyl titanate with a chelating agent to produce a product mixture comprising a titanium chelate and an alcohol; (2) optionally substantially removing the alcohol whereby an alcohol-reduced titanium chelate is produced; (3) contacting the product mixture or alcohol-reduced titanium chelate with a second alcohol to produce another alcohol-reduced titanium chelate; and optionally (4) reducing the alcohol content of the another alcohol-reduced titanium chelate to produce a substantially alcohol-free titanium chelate wherein the second alcohol is less volatile than the alcohol derived from the tetraalkyl titanate.
Also according to a third embodiment of the d invention, a process comprises (1) contacting a mixture comprising a tetraalkyl titanate and a second tetraalkyl titanate with a chelating agent to produce a product mixture comprising a titanium chelate and a mixture of alcohols derived from the tetraalkyl titanate and second tetraalkyl titanate; (2) substantially removing the mixture of alcohols to produce an alcohol-reduced titanium chelate; and optionally (3) reducing the alcohol content of the alcohol-free reduced titanium chelate to produce a substantially alcohol-free titanium chelate.
According to a fourth embodiment of the invention, a process comprises (1) contacting a single-alcohol titanium chelate with an alcohol, a second single-alcohol titanium chelate, or both to form a desired statistical mixture of (A), (B) and (C) disclosed above in the first embodiment of the invention; (2) substantially removing the mixture of alcohols to produce an alcohol-reduced titanium chelate; and optionally (3) reducing the alcohol content of the alcohol-reduced titanium chelate to produce a substantially alcohol-free titanium chelate.
The term xe2x80x9cless volatilexe2x80x9d refers to the boiling point of an alcohol being at least about 20xc2x0 C. higher than that of another alcohol, and the term xe2x80x9csimilar boiling pointsxe2x80x9d refers to boiling points of alcohols that are within about 5xc2x0 C.
According to the first embodiment, X is a radical derived from a chelating agent. A preferred chelating agent is an organic 1,3-dicarbonyl compound such as a diketone, a diester, a ketoester, and combinations of two or more thereof. A radical derived from any 1,3-diketone can be used. The preferred diketones include, but are not limited to, 2,4-pentanedione, 1,4-hexanedione, 1,3-pentanedione, 2,4-hexanedione, dipivaloyl methane, or combinations of two or more thereof.
Also, a radical derived from any 1,3-diester can be used. The preferred diesters include, but are not limited to, dimethyl malonate, diethyl malonate, or combinations thereof.
Similarly, a radical derived from any 1,3-ketoester can be used. The preferred ketoester include, but are not limited to, methyl acetoacetate, ethyl acetoacetate, isopropyl acetoacetate, butyl acetoacetate, and combinations of two or more thereof.
The most preferred chelating agent is 2,4-pentanedione, ethyl acetoacetate, or combinations thereof.
The preferred m is a number in the range from about 1.5 to about 2.5, preferably from 1.65 to about 2.2, more preferably from 1.8 to about 2.1, and most preferably about 1.9 to about 2. Those skilled in the art can recognize that in cases where m is not 2.0, structures A, B, and C will not have integral numbers of groups and actually are abbreviated shorthand representations of the actual components. In these cases, A, B, and C represent the average compositions of individual components having integral numbers of groups totaling 4 in number for all individual components.
The preferred R or R1 is hydrocarbyl radical having 1 to about 10 carbon atoms per radical including, but not limited to alkyl radical, cycloalkyl radical, alkylenyl radical, aryl radical, alkaryl radical, aralkyl radical, or combinations of two or more thereof. Examples of suitable radicals include, but are not limited to methyl, ethyl, propopyl, isopropyl, butyl, isobutyl, pentyl, sec-butyl, tert-butyl, and combinations of two or more thereof. However, R1 is different from R in the same titanium chelate complex.
Examples of mixed titanium chelates include, but are not limited to,
Ti(CH3C(O)CHC(O)CH3)1.95(OCH(CH3)2)2.05,
Ti(CH3C(O)CHC(O)CH3)1.95(OCH(CH3)2)1.025(OCH2CH2CH2CH3)1.025,
Ti(CH3C(O)CHC(O)CH3)1.95(OCH2CH2CH2CH3)2.05;
Ti(CH3C(O)CHC(O)CH3)1.95(OCH(CH3)2)2.05,
Ti(CH3C(O)CHC(O)CH3)1.95(OCH(CH3)2)1.025(OCH2CH3)1.025,
Ti(CH3C(O)CHC(O)CH3)1.95(OCH(CH3)2)2.05;
Ti(OC(CH3)CHC(O)CH3)1.95(OCH(CH3)2)2.05,
Ti(OC(CH3)CHC(O)CH3)1.95(OCH(CH3)2)1.025(OCH2CH2CH2CH3)1.025,
Ti(OC(CH3)CHC(O)CH3)1.95(OCH2CH2CH2CH3)2.05;
Ti(OC(CH3)CHC(O)CH3)1.95(OCH(CH3)2)2.05,
Ti(OC(CH3)CHC(O)CH3)1.95(OCH(CH3)2)1.025(OCH2CH3)1.025,
Ti(OC(CH3)CHC(O)CH3)1.95(OCH2CH3)2.05, and combinations of two or more thereof.
The composition can be characterized as having a low freezing point. The term xe2x80x9clowxe2x80x9d refers to a freezing point lower than about 30xc2x0 C., preferably about 20xc2x0 C., and most preferably 0xc2x0 C.
The composition can also be characterized as being essentially or substantially alcohol-free. That is, the alcohol content in the composition is about 5% or lower, preferably about 3% or lower, and most preferably about 2% or lower, by weight.
The composition of the titanium chelates of the present invention can be characterized as follows by high resolution nuclear magnetic resonance (NMR) spectroscopy following the method described below. It is to be understood that one skilled in the art may develop other methods of analysis that give an equivalent separation of the titanium chelate species involved, and that these are all within the scope of the inventive process.
A small portion of the sample is dissolved in deuterated benzene (or other suitable anhydrous NMR solvent) at a concentration typically employed for proton and carbon NMR analysis. The sample is scanned in both the proton (1H) and carbon (13C) frequency regions to generate proton and carbon spectra of the sample. In order to resolve the peaks for the individual components of the chelate mixtures, a high resolution NMR apparatus is employed. Any of the typical high field NMR instruments in common usage should generate acceptable spectra. The NMR analyses cited in the examples were performed on a Bruker NMR using the following conditions and parameters:
Carbon (13C) NMR spectra:
Frequency: 125.8 MHz
Acquisitions: 512
Pulse Width: 7.5 xcexcsec
Recycle Delay: 1 sec
Sweep Width: 39682.5
Acquisition time: 1.652 sec
Offset Frequency: 15928.7
Decoupling Mode: full 1H decoupling
Proton (1H) NMR spectra:
Frequency: 500.3 MHz
Acquisitions: 8
Pulse Width: 11.5 xcexcsec
Recycle Delay: 30 sec
Sweep Width: 10330.6
Acquisition time: 6.344 sec
Offset Frequency: 3066.2
The analyses are illustrated in the EXAMPLES section.
Wishing not to be bound by theory, it is believed that the composition disclosed herein is a statistical mixture of titanium chelates arising from free alcohol exchange. The composition can be analyzed in such a way as to distinguish between the individual chelates thereby making an essentially alcohol-free and uniform. By a statistical mixture is meant that the ratio of the above compounds A, B and C in the mixture is given by a:b:c where   a  =            relative  moles  of  titanium  chelate        A        =                  r1        2                              (                      r1            +            r2                    )                2              b  =            relative  moles  of  titanium  chelate        B        =                  2        ⁢        r1r2                              (                      r1            +            r2                    )                2              c  =            relative  moles  of  titanium  chelate        C        =                  r2        2                              (                      r1            +            r2                    )                2            
and where r1=total moles of (OR) in the mixture, and r2=total moles of (ORxe2x80x2) in the mixture. The ratio of r1 to r2 can be in the range of from about 0.5:1 to about 2:1 and preferably about 1:1. That is, the molar ratio of a:b can be in the range of from about 0.25:1 to about 1:1 and the molar ratio of c:b can be in the range of from about 0.25:1 to about 1:1. If the ratio of r1 to r2 is about 1:1, the percentage of a, b, and c are about 25%, 50%, and 25%, respectively.
The composition of the invention can be produced by any methods known to one skilled in the art. However, it is preferred it be produced by the processes disclosed in the invention.
According to the second embodiment of the invention, the tetraalkyl titanate, which can also be referred to by one skilled in the art as titanium tetraalkoxide, can have the formula of Ti(OR)4 where each R is individually a hydrocarbyl radical, as disclosed above, and can contain from 1 to about 10, preferably 1 to about 8, and most preferably 2 to 5 carbon atoms per radical and each R can be the same or different. Suitable tetraalkyl titanates include, but are not limited to, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, tetrabutyl titanate, tetraisobutyl titanate, tetra-tert-butyl titanate, tetrahexyl titanate, and combinations of two or more thereof. The preferred tetraalkyl titanate is tetraethyl titanate, tetraisopropyl titanate, or combinations thereof.
The chelating agent is the same as that disclosed in the first embodiment of the invention.
The product mixture comprises a titanium chelate and an alcohol. The titanium chelate comprises at least one compound selected from (A) and (C) disclosed in the first embodiment of the invention.
The alcohol produced is derived from the tetralkyl titanate and therefore has the same carbon number as the titanate. For example, if tetraethyl titanate is employed, the alcohol or third alcohol is ethanol and if tetraisopropyl titanate is used, it is isopropanol.
The second alcohol can be an alcohol depending on the type of tetraalkyl titanate used. The second alcohol can be any alcohol so long as the alcohol is less volatile than the alcohol derived from the tetraalkyl titanate and can produce a composition having the characteristics disclosed in the first embodiment of the invention. It can have the formula of R1OH such as propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol, isopentanol, hexanol, heptanol, or combinations of two or more thereof.
The molar ratio of tetraalkyl titanate to the chelating agent can be any ratio so long as the ratio can produce a composition having the characteristics disclosed in the first embodiment of the invention. Generally, the ratio is the one that produce mixed chelated having the numbers of m disclosed above.
The molar ratio of the second alcohol, to the tetraalkyl titanate can be any ratio so long as the ratio can produce a composition having the characteristics disclosed in the first embodiment of the invention.
Generally, the ratio can be in the range of from about 0.5:1 to about 4:1 preferably about 0.7:1 to about 1.2:1, and most preferably about 1:1.
The process can be carried out under any suitable condition effective to produce a product mixture comprising the composition disclosed in the first embodiment of the invention. A suitable condition for producing a titanium chelate from a tetraalkyl titanate can include a temperature below about 80, preferably below about 70, and most preferably below about 65xc2x0 C. under any pressure that can accommodate the temperature, preferably atmospheric pressure, for a period in the range of from about 0.1 to about 100, preferably about 0.5 to about 50, more preferably about 0.5 to about 30, and most preferably about 0.5 to about 15 minutes.
Removal of the alcohol liberated can be carried out by any means known to one skilled in the art to produce a second product mixture comprising an alcohol-reduced titanium chelate. For example, it can be carried out by distillation under a reduced pressure in the range of from about 1-200 mm Hg (0.13 to 26.7 kPa) for limited color formation and best alcohol removal. It can also be carried out by distillation at atmospheric pressure.
The another alcohol-reduced titanium chelate, or second product mixture produced from the alcohol-reduced titanium chelate and the second alcohol, can comprise a mixed titanium chelates comprising the radicals derived from the chelating agent and the second alcohol. This mixture can optionally be brought back to atmospheric pressure and, for example, further mixed such as by mechanical agitation at about 50 to about 80xc2x0 C. for about 1 minute or until the components have sufficient time to react to liberate more alcohol which can be removed as disclosed above.
Thereafter, the another alcohol-reduced titanium chelate can be further xe2x80x9cpolishedxe2x80x9d or xe2x80x9creducedxe2x80x9d by contacting it with an inert fluid. The reduction can be carried out (1 ) by contacting said substantially alcohol-free titanium chelate with an inert fluid, (2) under a reduced pressure, or (3) combination of (1) and (2). An inert fluid is one that does not react with a titanium chelate and can be liquid, gas, or combinations thereof. Examples of inert fluids include, but are not limited to nitrogen, carbon dioxide, and combinations thereof. Other methods such as, for example, vacuum, purging with nitrogen, vacuum cycling, or combinations of these and other methods that are apparent to those skilled in the art can also be used.
According to the third embodiment of the invention, the tetraalkyl titanate is the same as that disclosed above. The second tetraalkyl titanate can have the formula of Ti(OR1)4 where R1 is the same as that disclosed above. Example of suitable second tetraalkyl titanate can be the same as those illustrated above for the tetraalkyl titanate. However, when simultaneously used with the tetraalkyl titanate, the R1 in the second tetraalkyl titanate cannot be the same as R. The suitable chelating agents can also be the same as those disclosed above.
The molar ratio of the tetraalkyl titanate to second tetraalkyl titanate can be any ratios depending on the desired characteristics of the final product. For example, the ratio can be about 1:1. The conditions for contacting the mixture of tetraalkyl titanate and second tetraalkyl titanate with the chelating agent can be the same as the contacting of the tetraalkyl titanate with the chelating agent disclosed in the first embodiment of the invention. The alcohols generated correspond to the tetraalkyl titanate and the second tetraalkyl titanate used and can be removed by the process disclosed above in the second embodiment of the invention. Similarly, the alcohol-reduced titanium chelate can also be similarly xe2x80x9cpolishedxe2x80x9d as disclosed above.
According to the fourth embodiment of the invention, a process for producing an essentially alcohol-free statistical mixture of compounds of the formulas (A) TiXm(OR)4xe2x88x92m, (B) TiXm(OR)(4xe2x88x92m)/2(OR1)(4xe2x88x92m/2, and (C) TiXm(OR1)4xe2x88x92m comprises contacting a compound of formula (A) with at least sufficient amounts of an alcohol R1OH to form the desired statistical mixture of (A), (B) and (C), and removing the free alcohol from the mixture, using the process disclosed above, to a level of 2.0% by weight or lower in a manner that provides an essentially constant proportion of R to R1 by weight. Compound (A) can be produced by contacting a tetraalkyl titanate with a chelating agent as disclosed in the second and third embodiments of the invention. Contacting a compound of formula (A) with R1OH can be carried out under a suitable condition disclosed above in the second embodiment of the invention. Preferably, the product mixture is analyzed by a method that distinguishes between (A), (B) and (C). This is particularly desirable in initial production until satisfactory controls of product quality are established. Preferably the analysis is carried out by high resolution nuclear magnetic resonance.
Optionally, the essentially constant proportion of R to R1 by weight can be obtained by careful control of the distillation temperature, pressure. reflux ratio and other variables, once the product composition is established and confirmed by an analytical method that distinguishes between (A), (B) and (C).
The processes of the invention requires a one pot reaction and no blending operation, resulting in reduced cycle time, increased productivity, and reduced cost due to elimination of intermediate storage and mixing steps.
The process can be depicted as Ti(OR)4+Ti(OR1)4+4Xxe2x86x92 2TiX2(OR)(OR1)+2ROH+2R1OH for the case in which m=2 and TiX2(OR)(OR1) is a shorthand representation of the previously described statistical mixture.